The present invention relates to an image reader for obtaining the image data for image forming apparatus of, for example, electrophotographic system and to an image forming apparatus that is provided with the image reader.
The image reader photoelectrically converts reflected light obtained by illuminating the object to be read such as a sheet-form document or book, or solid body, and so forth by the image reader sensor such as a CCD sensor, and the like, and output the image data.
For the image reading method by the image reader, there are two systems: one a flat bed mode in which a original document is allowed to be at rest on a transparent document holding section (transparent glass) and an optical system such as a lighting device and a mirror, and the like or an image reader sensor is moved along the transparent glass and the other a sheet-through mode in which an optical system such as a mirror, and the like or image reader sensor and the illuminating device are fixed to a specified location in advance, the reading position is defined, sheet-form objects to be read are transferred successively to the reading position. Today, in many of the image readers, in order to enable the above-mentioned two reading systems, together with the transparent glass, a reading position for sheet-through that enables sheet-through is provided. Consequently, the reading position for sheet-through is generally defined to be the specified position further remote from the head end of the transparent glass which is the acceleration section used for acceleration when the optical system such as an illuminating device and a mirror, and the like or an image reader sensor travels in the flat bed mode.
Next, the basic configuration of the image reader of a flat bed mode that enables sheet-through will be described.
When the flat bed mode is adopted, the following system is used; a carriage holding the illuminating device and mirror, and the like that can illuminate the reading width, the total length of one side (width) direction of transparent glass is allowed to travel at a specified speed with a specified interval made with the transparent glass held along the reading length, the total length of the other one side (length) that intersects the reading width at right angles, and using a lens, and the like, the reflected light from the object to be read (illuminated by the illuminating device) is transmitted to the CCD sensor fixed to the position which do not interfere with the carriage travel.
On the other hand, when the image data of the sheet-form original document is obtained by the sheet-through mode, the carriage is fixed opposite to the transparent glass at the specified position where the reflected light from the reading position is able to be guided to the CCD sensor and the object to be read is conveyed to the reading position successively.
Now, in the image reader, in order to correct shading when the image of the object to be read is converted to the image data, the shading data is generated from the reflected light obtained by illuminating the white board of the specified brightness that serves as the standard for shading correction and then, shading of the read image is carried out. In addition, when the shading data is generated, the data for several lines (in the length direction) are generally balanced for each pixel (in the width direction) to prevent influences of dirt, dust, and the like (dirt, dust, and the like are read as the image).
Consequently, in general, while the carriage is being moved at the constant speed, the reflected light is read from the white board for shading correction. By the way, in the image reader as described above, the carriage is accelerated at the specified acceleration in such a manner that the carriage is moved along the transparent glass, that is, the object to be read (in such a manner that the carriage reaches to the specified speed (constant speed) when the carriage in motion reaches the glass end section) as the carriage begins to travel from the home position, the travel starting position. By the way, the home position is, in general, set at the specified location between the white board for shading correction and the reading position (for the sheet-through mode). Consequently, the time for reading the reflected light from the white board for individual lines (in the length direction) is set to the constant value in accordance with the cycle of the horizontal (reading length) synchronous signal (referred to as the xe2x80x9cH-SYNC signalxe2x80x9d) irrespective of the reading speed, that is, the speed at which the carriage is moved in the reading length (horizontal) direction.
However, when the home position is located in the vicinity of the white board as described above, there is a problem in that the distance between the home position and the transparent glass head end is long and the time required for first scan is long (first scan is unable to be shortened) because in the flat bed mode, the carriage is maintained temporarily to the constant speed for acquiring the shading data by the white board in the midst of acceleration from the home position and then, is accelerated to the reading speed in the section up to the transparent glass head end (there are cases in which the carriage is accelerated to the reading speed when the carriage is allowed to pass the white board).
In addition, when the image data is obtained by sheet-through in the image reader described above, there is also a problem in that the first scan time becomes still longer than in the flat bed mode because the carriage must be returned to the reading position for sheet-through after the carriage is temporarily allowed to pass the shading position opposite to the white board to obtain the shading data.
By the way, in the high-speed image reader of the flat bed mode, there is a case in which the carriage is unable to be accelerated to the specified reading speed in the section up to the transparent glass head end because the carriage is moved at a constant speed in the section opposite to the white board in order to obtain the shading data, and as a result, a problem in that the size of the image reader becomes large arises.
Accordingly, it is an object of the present invention to provide an image reader that can shorten the first scanning time required for the carriage to move from the home position to the start of image reading in an image reader provided with a carriage to move the illuminating device.
It is another object of the present invention to provide an image reader comprising:
a CCD sensor for converting an image of an object to be read to image data of electrical signals;
a transparent glass for holding the object to be read;
a mirror set includes one or more mirrors, and is able to move along the transparent glass, for transmitting the image of the object to be read to the CCD sensor;
an illuminating device is moved along the transparent glass together with the mirror set and illuminates the object to be read held to the transparent glass;
a carriage member for supporting the mirror set and the illuminating device, which moves at a specified speed along the transparent glass by external driving force, and for indicating an own position by a marker member mounted on its own specified position;
a white reference provider for providing white reflected light that serves as a reference for defining a threshold level when the CCD sensor outputs the image data;
a home position sensor for detecting the marker member of the carriage member and setting the wait position of the mirror set and the illuminating device;
a reading window that is arranged at a specified position in a direction away from the transparent glass with the white reference provider set at the center in a plane defined by the white reference provider as well as the transparent glass and enables the image of the object to be read to be transmitted to the CCD sensor through the mirror set by feeding of the object to be read independently from the object to be read set on the transparent glass; and
a drive unit for moving the carriage member at a predetermined speed and setting the position of the carriage member in such a manner that, at the wait time, the reflected light from the white reference provider is guided to the mirror of the mirror set supported on the carriage member, to which the reflected light from the object to be read is first transmitted.
It is a further object of the present invention to provide an image reader comprising:
a CCD sensor for converting an image of the object to be read to the image data of electrical signals;
a transparent glass for holding the object to be read;
a mirror set includes one or more mirrors, and is able to move along the transparent glass, for transmitting the image of the object to be read to the CCD sensor;
an illuminating device is moved along the transparent glass together with the mirror set and illuminates the object to be read held to the transparent glass;
a carriage member for supporting the mirror set and the illuminating device, which moves at a specified speed along the transparent glass by the external driving force, for indicating an own position by a marker member mounted on its own specified position;
a white reference provider for providing the white reflected light that serves as a reference for defining the threshold level when the CCD sensor outputs the image data;
a home position sensor for detecting the marker member of the carriage member and setting the wait position of the mirror set and the illuminating device;
a reading window that is arranged at a specified position in the direction away from the transparent glass with the white reference provider set at the center in a plane defined by the white reference provider as well as the transparent glass and enables the image of the object to be read to be transmitted to the CCD sensor through the mirror set by feeding of the object to be read independently from the object to be read set on the transparent glass; and
a drive unit for moving the carriage member at a specified speed in the section opposite to the transparent glass, and at the wait time, setting the position of the carriage member in such a manner that the reflected light from the white reference provider is guided to the mirror, to which the reflected light from the object to be read of one or more mirrors of the mirror set supported on the carriage member is first transmitted, and moving the carriage member towards the transparent glass side and accelerating the carriage member to the specified speed until the carriage member faces opposite to the transparent glass head end when the instruction is given to read the image of the object to be read set on the transparent glass, and driving the carriage member to the reading window, that is, towards the direction opposite to the transparent glass and stopping the carriage member at the position opposite to the reading window.
It is an additional object of the present invention to provide a method for driving an image reader that guides the reflected light from the white reference provider to the mirror of one or more mirrors of the image reader to which the reflected light from the object to be read is first transmitted and defines the threshold level comprising the steps of:
moving the mirror set that can transmit the reflected light from the band-form region illuminated by the illuminating device that can provide a band-form illuminated light extended in the first direction and having the specified length in the second direction intersecting to the first direction by the use of the mirror set with a plurality of mirrors extended in the first direction and having a specified length in the second direction as well as the carriage member containing the illuminating device along the image of the object to be read,
moving the carriage member at the wait time in such a manner that the rough center of the mirror in the second direction to which the reflected light is first transmitted from the object to be read of the mirror set is opposite to the rough center of the white reference provider in the second direction for providing the white reflected light that serves as the reference to define the threshold level for CCD sensor to output the image data, and moving the carriage member at a specified speed in the section opposite to the transparent glass,
moving the carriage member towards the transparent glass side and accelerating the carriage member to the specified speed until the carriage member becomes opposite to the transparent glass head end when the instruction is given to read the image of the object to be read set to the transparent glass, and
driving the carriage member towards the reading window and stopping the carriage member at the position opposite to the reading window when the instruction is given to read the image of the object to be read conveyed to the reading window.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.